Correlation of radiographic renal cell carcinoma tumor volume utilizing computed tomography and magnetic resonance imaging compared with pathological tumor volume

Objective. New evidence suggests that three-dimensional pathological tumor volume (TV) provides additional prognostic information in renal cell carcinoma (RCC) to that provided by tumor size alone. The aim of this study was to assess the correlation between radiographic TV, by computed tomography (CT) and magnetic resonance imaging (MRI), and pathological tumor volume (TV). Material and methods. Pathological TV from 143 patients treated with surgical removal for unilateral RCC was compared with radiographic TV. Measurements were taken by one central pathologist and one radiologist, who were blinded to each other's findings. The TV for each modality was calculated using the equation for measuring the volume of an ellipsoid: π/6(Length × Width × Height). Results. No statistical differences were noted for relevant clinicopathological covariates between patients who had CT scan or MRI. The correlation coefficient for pathological TV was similar for MRI (0.97) and CT (0.98), although the correlation was lowest for those patients with the smallest tumors (0.82 for pT1a). The TV correlation was weaker among non-obese patients [0.99 for body mass index (BMI) >30 vs 0.89 for BMI <30]. Gender, tumor grade and tumor subtype did not affect TV correlation. Incongruence between radiographic TV and pathological TV is due to overestimation of TV by radiographic imaging. Conclusions. There was a strong correlation between RCC TV on preoperative images (CT and MRI) compared with pathological TV. This correlation was diminished for patients with smaller tumors. Future investigations are needed to validate this observation and more directly explore the ability of radiographic TV to predict RCC progression and patient outcome.